The present invention to improvements in papermaking machines, and more particularly to an improved threading system for a winder or other paper handling area where a sheet must be threaded along a paper machine processing path.
For threading the lead end of a sheet through a processing path in a papermaking machine, the lead edge of the paper web is conventionally moved horizontally or in a downward direction along pans utilizing air showers. This method, however, will not work if the leading edge of the paper is to be transported in an upward direction. Also, difficulty is encountered when the sheet must be threaded through a tortuous path involving being carried over a number of rolls which are not arranged in a straightline. During the threading operation it is necessary to grip the lead end of a web and transport it along a processing path which may be across spaced rolls or along a belt or over the surface of a large roll. It is essential to satisfactory threading to have positive control of the lead end of the sheet so that it is not lost when making a sudden turn or carrying the sheet along an outwardly extending curve. It is also desirable that the sheet be held reasonably taut so that it does not wrinkle or flutter and so that control of the sheet is not lost.
An example of the need for a threading device to carry the lead end of the sheet is in a winder. The device which is used for threading the lead end of the sheet should be of a construction so that it does not get in the way of normal operating mechanisms and should be of a construction such that it can be brought into an existing papermaking machine without requiring alteration of the machine and so that the machine can be designed without modification or consideration as to providing space for the threading device. The threading device should be such that it can be quickly and easily brought into play when threading is required and moved out of the way as soon as the threading is completed and the machine is brought into normal operation. Devices heretofore available have not been readily capable of carrying a web through all types of paths including upwardly extending paths and have not had the flexibility and capability of handling situations as above described.
It is accordingly an object of the present invention to provide an improved threading mechanism for carrying the lead end of a sheet through a path in a papermaking machine which avoids disadvantages encountered in systems heretofore available. A further object of the invention is to provide an improved threading device which is relatively inexpensive and has a long operating life not requiring repair or maintenance.
A further object of the invention is to provide a sheet threading device which makes it possible to quickly and surely grip the lead end of a traveling sheet and which automatically releases the sheet after it has completed threading it through the desired path.
Other objects, advantages and features, as well as equivalent structures which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawings, in which: